A heat wave is caused when an area of high pressure in the atmosphere becomes stationary over a location. Due to the natural effects of high pressure, the area receives little to no wind and this causes the air to remain stationary. In a developed area, the chemicals released into the air, through industry or the burning of fossil fuels from transport, stay in the environment and build up.
The other major feature of an area of high pressure is increased day time temperatures as there is little cloud cover stopping the sun from shining down. This then warms the chemicals in the area and effectively cooks them until they form smog. Smog is potentially lethal and can cause an array of health effects. Smog caused twelve thousand deaths in London in 1952 when it was present for just four days.
Heat waves effectively bring a pocket of air to a complete standstill. This stops the natural air currents from dissipating the general build up of chemicals in the air and the natural vertical circulation of the air stops occurring. Chemicals are sent into the air from many every day things, such as lighting a fire, using a car or even agriculture such as farm animals. When the industrialisation of production is included in this, the air becomes full of chemicals. Normally these would be blown around by air currents and would dissipate; however in an area that is experiencing a heat wave, these chemicals stay in the local environment and mix together with the aid of the sunlight. This chemical soup then mixes with any water in the air and forms smog, a mix of smoke and fog.
Smog is common in many cities and highly developed areas and normally doesn’t cause much of a problem because of the naturally movement of the air. It is only when the smog becomes stationary that it causes real problems. In a heat wave, the natural vertical circulation of air stops occurring, which means valleys and bowls are highly affected in these periods. Smog becomes stuck in an area by the natural geographical features of the area. Los Angeles suffers majorly because of the surrounding mountains and sheer number of vehicles and industry running there.
The Great Smog of 1952 happened in London, England and, as stated previously, is believed to have caused twelve thousand deaths. The smog darkened the streets of London for just four days before being dissipated by other weather conditions. This just goes to show how dangerous smog can be. After this London introduced a Clean Air Act and created smokeless zones. Smog in London still occurs from traffic, but the amount is much smaller and the days of great smogs are long gone.
Heat waves cause air pollution to mount up because the conditions of a heat wave completely limit air movement and cause long periods of bright sunshine. These factors, mixing with the water in the air create smog which is dangerous to health and makes the quality of air much worse.